Lawns are the largest “crop” in the US. In 2005, NASA estimated that lawns covered over 40 million acres of US soil. If that number is correct, there is more lawn grass in the US than the 8 largest irrigated crops combined!

Most lawns in Wyoming are some combination of Kentucky bluegrass and fescue. We spend a lot of resources fertilizing, watering, and mowing our lawns. Is there any value in all of that grass?

Horses should never be fed grass clippings! Because of the short fiber length, most lawn grass clippings will pass through the digestive system very quickly. A pile of fresh grass clippings is too tempting to resist, and most horses would gorge themselves given the opportunity. Both of these factors can lead to excess fermentation in the hind gut, and colic. Horses are also susceptible to botulism which can develop in anaerobic conditions (i.e. a pile of grass clippings).

Cattle and sheep have a different digestive system and are not at risk of colic or botulism. However, that does not mean throwing grass clippings into the feed bunk is always a good idea.

Nitrate ToxicityNitrate toxicity is a risk with many forages, including grass clippings. Bacteria in the guts of ruminants convert the nitrate in forage into ammonia which is used to make protein for bacterial growth and reproduction. Nitrite is produced as an intermediate compound created in this process, and can inhibit the ability of the blood to transport oxygen. Toxicity depends on the nitrate concentration of the forage and rate of consumption. For example, an animal that consumes high nitrate forage quickly is more at risk of poisoning than an animal that consumes this same forage over a longer period of time.

Excessive nitrates will most often accumulate in the stalks or stems of plants under stress.

Stressful conditions include drought or cold weather, herbicides, and disease. While levels of nitrogen in the soil are also a factor in nitrate accumulation, it is not as important as plant stress. Allowing fresh grass (i.e. green chop or grass clippings) to heat up before feeding greatly increases the levels of toxic nitrite (due to bacterial activity in the pile) and can turn an otherwise safe feed deadly.

Considering this, the highest risk of nitrate toxicity from grass clippings would come from a heavily fertilized lawn under stress, that was stored in a pile and allowed to heat up before feeding, and then was consumed quickly by livestock and not mixed with other forages.

If you are concerned about the nitrate concentration of your lawn grass, or any other forages, send a sample into a lab for analysis. It will cost you less than $20. If the grass is high in nitrates, you may still be able to feed it as long as it is mixed thoroughly with other feeds.

SilageEnsiling forages can reduce nitrate levels by 40 to 60%. However, it is still a good idea to test the silage for nitrates before feeding.

Ensiling is a way of storing forages in anaerobic conditions (no oxygen) that preserves their nutritional value. Bacteria ferment the sugars and starches in the grass and produce lactic and acetic acids. Successful ensiling requires grass that has a moisture content of 60-70% and a sealed environment that excludes oxygen. After several weeks of fermenting, silage should have a pH below 4.5, a slight vinegar odor, and be light green to yellow in color.

Pesticides and Poisonous PlantsIf the area where you are collecting clippings has been sprayed with any pesticides be sure and thoroughly read the label to determine if the grass is safe to feed to livestock. Some herbicides will pass through the gut without harming the animals and still be active when excreted in manure.

There are many plants that are poisonous to livestock. If you mow an area with heavy weeds, tree leaves, or pine needles it would be wise to put that load in the compost pile instead of the feed bunk.

Fall is a good time to think about soil management. You can collect soil samples, decide on management changes for the next growing season, and have the winter to do some reading and research.

When it comes to soil management, ask yourself three questions:

What do I have?

What does my crop need?

What changes can I make to increase profitability?

In answering these questions, think about both soil conditions and soil nutrients. For example, grasses are more tolerant of saline soil condition than alfalfa, but does not have the deep taproots to access nutrients and water in the subsoil like alfalfa.

What do I have?A soil test can tell you several important things about your soil, including nutrient and organic matter status, pH, and salt content. Most labs will provide fertilizer recommendations based on crops, yield goals, irrigation, and previous manure applications. A few things to keep in mind:

Alfalfa produces it's own nitrogen (N) through a symbiotic relationship with Rhizobium bacteria. It is rarely, if ever, economical to apply N fertilizer to alfalfa.

Test soils for nitrate annually in the spring every year before applying N fertilizer. N is very mobile in the soil and quickly lost by leaching due to irrigation or precipitation.

Test soils every 2-3 years for phosphorus (P), potassium (K), micronutrients, organic matter, pH, and soluble salts. If you are making significant management changes, or monitoring a field for high salts or pH, consider testing more frequently.

While Wyoming no longer has a soil test lab, there are labs in Nebraska, Idaho, and Utah. It is best to stick with the same lab over time to reduce variability in results and fertilizer recommendations.

Just getting out and digging a hole is useful too! Pay attention to the color and smell of the soil, presence of earthworms, and rooting depth. This can reveal important information about soil carbon, compaction, and general soil health.

What changes can I make to increase profitability?When making changes to your production system, be it tillage, fertilizer, or cropping systems,keep good records. Remember, if you don't measure it you can't manage it! Depending on your soils and what your crop needs, here are some changes to consider:

Decease fertilizer applications to reduce costs or wasted nutrients.

Increase fertilizer use to reach optimum yields.

Change the timing of fertilizer or manure applications to more closely match plant needs.

Reduce soil compaction to increase rooting depth, and plant access to water and nutrients.

Use manure to build soil organic matter while providing all essential plant nutrients.

The Wyoming Ranch Tools website has some useful tools that can help you determine if the benefits of adding fertilizer are worth the additional costs, based on hay prices, input costs, and labor. Considering hiring a custom operator to do some of the work for you, or putting your tractor to work for someone else? Read my blog post on custom rates.

With the exception of some carbon, nitrogen, hydrogen, and oxygen, plants get their essential nutrients from the soil. Therefore, if the soil is deficient in nutrients the plants will also be deficient. That being said, not all soil nutrients are plant available due to many complex biological and chemical interactions between soil minerals and organic matter. This is especially the case with phosphorus, zinc, iron, manganese and copper.

Plant nutrients are often categorized as macro-nutrients or micro-nutrients, depending on how much of a particular nutrient plants need. While there is some variation between species of plants, the chart below helps illustrate the difference in nutrient needs for most agricultural crops.